Large water filtration systems frequently include one or more stages of filtration that clean the influent (typically water) to a sufficient level to allow for the discharge of the influent into a natural body of water such as a lake or river. In regions where water is scarce, it may be desirable to further filter the water to allow for “reuse” of the water.
Many wastewater treatment plants utilize a disc filter system to filter water. Such systems typically include a plurality of discs each including a plurality of filter segments. Each filter segment includes a pair of filter panels which are spaced apart and arranged on an outer surface of a drum. A cap is attached to the top of each pair of filter panels to thus form a cavity for receiving water. Each filter panel includes filter media, such as finely woven cloth for filtering water.
In operation, the drum is rotated and the water to be filtered is introduced into the drum. The water then exits through ducts in the drum and flows into one or more filter segment cavities. The water in the filter segment cavities is then filtered through the media of the filter panels to provide filtered water. The filtered water is then collected in a chamber and exits the disc filter through an effluent pipe. Particulates which are filtered out by the filter panels remain within the filter segments on the inside surface of the filter media of the filter panels. A spray device is used to spray the panels with water to dislodge the particulates and clean the filter media. The particulates are then collected onto a trough and are removed from the disc filter system.
Each filter panel is attached to the drum by a filter support arrangement. Each filter support holds at least a side portion of an associated filter panel. The filter supports do not have openings and thus do not allow fluid communication between adjacent filter segments. Further, the characteristics of filter media in the filter panels is such that air cannot readily pass through the filter media when the filter media is wet. Therefore, air cannot be readily vented from the filter cavity during the filtering process. As a result, a vacuum is formed as each filter segment transitions from being submerged in water to being positioned out of the water. As the drum continues to rotate, air from drum headspace rushes in to the filter segment and creates turbulence that washes off particulates captured by the filter media. The particulates then undesirably fall back into the drum, resulting in dirtier water. Therefore, there is a need to relieve the vacuum that is formed in the filter segment during the filtering process.